1. Field of the Invention
The present invention relates to a thin film magnetic head substrate, and more particularly, to a thin film magnetic head substrate including a monitor element used for the lapping process to form a medium-facing surface on a head element portion.
2. Description of the Related Art
A thin film magnetic head is produced by arranging head element portions (head element structures), each formed of at least a stack of a read element and a write element on a single wafer (substrate), in a plurality of rows. The wafer is then cut and lapped to form the medium-facing surface (to define the element height); thus providing a bar-like thin film magnetic head substrate having a plurality of the head element portions arranged in a single row on the wafer or an individual (chip-like) thin film magnetic head having one head element portion formed on the wafer.
The lapping process for forming the medium-facing surface is performed to lap the wafer end surface in the element height direction while applying the electric current to the read element or the read monitor element simultaneously produced to detect the element resistance. The lapping process ends when the element resistance reaches the specified value. In the case where the element height is specified based on the resistance value of the read element or the read monitor element, it is difficult to obtain an actual dimension of the height of the write element. The element height of the write element is required to be accurately specified as it is an important factor to contribute to the write property. The art described below has been proposed to form the read monitor elements and the write monitor elements each changing the resistance value in accordance with the element height of the read element and the write element simultaneously. The lapping is performed up to the position where the properties required for the respective elements are obtained while detecting each element resistance against the current applied to the respective read and write monitor elements.
The thin film magnetic head with monitor elements used for the aforementioned lapping process control has been disclosed in U.S. Pat. No. 6,884,148 as Patent Document 1.
In the aforementioned art where the monitor elements are provided individually for the read element and the write element, a wider space is required to accommodate not only the increased monitor elements but also the electrode terminals for those elements. Widening of the space for accommodating the monitor elements is undesirable because the number of the head element portions that may be formed on the single wafer is reduced, thus deteriorating the productivity. There is a need for arranging monitor elements individually provided for read and write elements to save space.